There is overwhelming evidence that polybrominated diphenyl-ethers (PBDEs) and polybrominate pyrroles (PBPs) are bioaccumulating in the marine food chain and that these compounds are of biological origin. While the harmful effects of halogenated organic compounds (HOCs) on humans and the environment are only beginning to be understood, their structural similarities to anthropogenic pollutants suggest they represent an emerging and poorly characterized group of marine toxins. The overall goal of Project 1 is to identify the biological sources of PBDEs and PBPs in the Southern California Bight. This goal will be accomplished through a comprehensive sampling paradigm targeting bulk and size-fractionated plankton, sediments, benthic algae, and filter feeding invertebrates. Sampling efforts will capitalize on small boat and shipboard resources available through SIO and expertise provided by plankton expert Melissa Carter (SIO) and collaborators at the J. Craig Venter Institute (see letter of support from L. Zeigler). Project 1 activities will be tightly integrated with Project 3 and the Analytical Core, which will identify and quantify PBDEs and PBPs in the samples collected. This information will be used to link specific compounds with sample types and to guide subsequent microbial cultivation efforts and cultivation-independent diversity studies. Metagenomic data generated from Project 2 will, provide a complimentary analysis of microbial community composition and insight into the biosynthetic genes associated with HOC production. This information will be used in quantitative PCR and CARD-FISH studies designed to assess the numbers and location of HOC-producing bacteria and relevant biosynthetic genes in different sample types. HOCs that cannot be identified by Project 3 based on comparisons with reference data will be isolated, structurally characterized, and provided to Project 3 for toxicological evaluation and as GC-MS standards. Select PBPs previously identified from environmental samples will be synthesized to provide baseline toxicological data and GC-MS standards. A major effort will be placed on the cultivation of HOC-producing bacteria, as there is considerable preliminary evidence that they represent an important biological source of these compounds. This research represents the first major effort to identify the biological sources and sinks of an increasingly important group of marine pollutants in a major US coastal environment.